Use auto profiler to set branch weights

[Eric Christopher]

A few general comments:

A comment would be nice for dumpInstrumentedInsns that we don't need
DEBUG for the dbg() statements.

It's handy if the test case has the C/C++/etc code used to reproduce
inside it in case something changes or someone wants to take a fresh
look. Also a comment with what you're testing and where so that people
don't have to guess.

It looks like you're doing the sample information based on line?

-eric



On Fri, Oct 18, 2013 at 3:50 PM, Diego Novillo <dnovillo at google.com> wrote:
> This patch converts instruction samples into branch weights. It
> does a fairly simplistic conversion:
>
> Given a multi-way branch instruction, it calculates the weight of
> each branch based on the maximum sample count gathered from each
> target basic block.
>
> Note that this assignment of branch weights is somewhat lossy and can be
> misleading. If a basic block has more than one incoming branch, all the
> incoming branches will get the same weight. In reality, it may be that
> only one of them is the most heavily taken branch.
>
> I will adjust this assignment in subsequent patches.
>
> Chandler, at this point it may be more convenient to send a full
> patch including all the partial patches I've sent before. If you
> prefer that, please let me know.
>
> All my questions re. guidance still apply to this patch. I've
> focused on getting *something* going, so there are many rough
> corners and incompleteness.
>
>
> Thanks.  Diego.
>
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